The Wnt pathway antagonist DKK1 is upregulated by amino acid deficiency in a human colon cancer cell line.

Abstract

Amino acid response (AAR) pathway is activated when cells are deprived of amino acid. Activation of the AAR pathway causes upregulation of downstream genes. In the present study, we observed that the Wnt signaling pathway, playing an important role in development and tumorigenesis, is involved in this process. DKK1, an antagonist of the Wnt pathway, was significantly induced at mRNA level in the human colon cancer cell line SW480 after the removal of total amino acids and reached the peak of expression at 8hr. A key target of the AAR pathway, asparagine synthetase was also upregulated. Blocking the availability of a single amino acid histidine with histidinol also caused activation of the AAR pathway and led to an increase in DKK1 expression that is similar to total amino acid limitation. Blocking of the phosphorylation of ERk1/2 abolished the induction of DKK1. Analysis of mRNA stability showed that the induction was partly due to transcriptional regulation. Luciferase reporter assay was conducted to map the basal promoter and amino acid responsive element. Chromatin Immunoprecipitation assay was used to define transcription factor binding and chromatin modification induced by amino acid limitation. In conclusion, the present study showed that the Wnt signaling pathway is a potential downstream target of AAR pathway through the regulation of one of the antagonist, DKK1.Grant Funding SourceCIAF